High sensitivity-high resonance frequency vortex shedding flowmeter

Abstract

This invention discloses a vortex sensor for detecting vortices generated by a bluff body immersed in a fluid stream, which vortex sensor comprises an elongated or planar member receiving fluid dynamic forces associated with the vortices and a transducer connected thereto, wherein at least one extremity of the elongated or planar member is secured to the wall structure of the flow passage, while the other unsecured extremity of the elongated or planar member or an extension thereof is connected to the force receiving member of a transducer. The secured extremity of the elongated or planar member contributes to a high resonance frequency thereof well above the vortex shedding frequency ranges, while the other unsecured extremity contributes to a high sensitivity in the vortex sensing as that extremity connected to the transducer transmits all of the stress and/or strain generated by the fluid dynamic forces associated with the vortices to the force receiving member of the transducer.

The embodiments of the invention, in which an exclusive property or priviledge is claimed, are defined as follows: 
     
       1. A device for measuring fluid flow comprising in combination: (a) a body including a flow passage;   (b) a bluff body of elongated shape disposed across a first cross section of the flow passage;   (c) a planar member disposed at least partially across a second cross section of the flow passage generally parallel to the bluff body on a plane generally parallel to the central axis of the flow passage wherein at least one extremity of the planar member is secured to the body at least in part; and   (d) a transducer including a force receiving member connected to a laterally deflective portion of the planar member by a mechanical coupling that transmits stress from the planar member to the force receiving member and produces a bending moment in the force receiving member; wherein alternating lift force on the planar member associated with vortices shed from the bluff body generates a fluctuating electrical signal from the transducer as a measure of fluid flow moving through the flow passage, wherein the volume flow rate of the fluid is determined from the frequency of the fluctuating electric signal and the mass flow rate of the fluid is determined from a combination of the frequency and amplitude of the fluctuating electrical signal.     
     
     
       2. A combination as set forth in claim 1 wherein said combination includes means for exerting a lateral force of known magnitude on the planar member in pulses and means for measuring the amplitude of electrical signal from the transducer generated by said lateral force, wherein the ratio of the magnitude of said lateral force to the amplitude of said electrical signal generated by said lateral force is used as a calibration standard in determining the mass flow rate of the fluid from the combination of the frequency and amplitude of the fluctuating electrical signal. 
     
     
       3. A device for measuring fluid flow comprising in combination: (a) a body including a flow passage;   (b) a bluff body of elongated shape disposed across a first cross section of the flow passage;   (c) a planar member disposed at least partially across a second cross section of the flow passage generally parallel to the bluff body on a plane generally parallel to the central axis of the flow passage wherein at least one extremity of the planar member is secured to the body at least in part; and   (d) a transducer including a force receiving member connected to a laterally deflective portion of the planar member by a mechanical coupling that transmits stress from the planar member to the force receiving member and produces a bending moment in the force receiving member, wherein the force receiving member extends from a thin wall of a container vessel housing at least one Piezo electric element pressed against the thin wall; wherein alternating lift force on the planar member associated with vortices shed from the bluff body generates fluctuating electrical signals as a measure of fluid flow moving through the flow passage.     
     
     
       4. A device for measuring fluid flow comprising in combination: (a) a body including a flow passage;   (b) a bluff body of elongated shape disposed across a first cross section of the flow passage;   (c) a planar member disposed at least partially across a second cross section of the flow passage generally parallel to the bluff body on a plane generally parallel to the central axis of the flow passage wherein at least one extemity of the planar member is secured to the body at least in part; and   (d) a transducer including a force receiving member connected to a laterally deflective portion of the planar member by a mechanical coupling that transmits stress from the planar member to the force receiving member and produces a bending moment in the force receiving member, wherein the planar member includes at least one slit partially separating said deflective portion from secured portion of the planar member; wherein alternating lift force on the planar member associated with vortices shed from the bluff body generates fluctuating electrical signals as a measure of fluid flow moving through the flow passage.     
     
     
       5. A device for measuring fluid flow comprising in combination: (a) a body incuding a flow passage;   (b) a bluff body of elongated shape disposed across a first cross section of the flow passage;   (c) a planar member disposed at least partially across a second cross section of the flow passage generally parallel to the bluff body on a plane generally parallel to the central axis of the flow passage wherein at least one extremity of the planar member is secured to the body at least in part; and   (d) a transducer including a force receiving member connected to a laterally deflective portion of the other extremity of the planar member opposite to said one extremity by a mechanical coupling that transmits stress from the planar member to the force transmitting member and produces a bending moment in the force receiving member, wherein the planar member includes a slit partially separating said deflective portion connected to the force receiving member from secured portion of the planar member; wherein alternating lift force on the planar member associated with vortices shed from the bluff body generates fluctuating electrical signals as a measure of fluid flow moving through the flow passage.     
     
     
       6. A device for measuring fluid flow comprising in combination: (a) a body including a flow passage;   (b) a bluff body of elongated shape disposed across a first cross section of the flow passage;   (c) a planar member disposed at least partially across a second cross section of the flow passage generally parallel to the bluff body on a plane generally parallel to the central axis of the flow passage wherein at least one extremity of the planar member is secured to the body at least in part; and   (d) a transducer including a force receiving member connected to a deflective portion of said one extremity of the planar member partially secured to the body by a mechanical coupling that transmits stress from the planar member to the force receiving member and produces a bending moment in the force receiving member, wherein the planar member includes a slit partially separating one portion of the planar member connected to the force receiving member from the other portion of the planar member secured to the body; wherein alternating lift force on the planar member associated with vortices shed from the bluff generates fluctuating electrical signals as a measure of fluid flow moving through the flow passage.     
     
     
       7. A device for measuring fluid flow comprising in combination: (a) a body including a flow passage;   (b) a bluff body of elongated shape disposed across a first cross section of the flow passage;   (c) a planar member disposed at least partially across a second cross section of the flow passage generally parallel to the bluff body on a plane generally parallel to the central axis of the flow passage wherein at least one extremity of the planar member is secured to the body at least in part, wherein at least a portion of one extremity of the planar member and one portion of the other extremity of the planar member opposite to said one extremity are secured to the body; and   (d) a transducer including a force receiving member connected to a deflective portion of said the other extremity of the planar member by a mechanical coupling that transmits stress from the planar member to the force receiving member and produces a bending moment in the force receiving member; wherein alternating lift force on the planar member associated with vortices shed from the bluff body generates fluctuating electrical signals as a measure of fluid flow moving through the flow passage.     
     
     
       8. A combination as set forth in claim 7 wherein the planar member includes at least one slit partially separating one portion of the planar member connected to the force receiving member from the other portion secured to the body. 
     
     
       9. A device for measuring fluid flow comprising in combination: (a) a body including a flow passage;   (b) a bluff body of elongated shape disposed across a first cross section of the flow passage;   (c) a planar member disposed at least partially across a second cross section of the flow passage generally parallel to the bluff body on a plane generally parallel to the central axis of the flow passage wherein at least one extremity of the planar member is secured to the body at least in part; and   (d) a transducer including a force receiving member connected to a midsection of the planar member by a mechanical coupling that transmits stress from the planar member to the force receiving member and produces a bending moment in the force receiving member; wherein alternating lift force on the planar member associated with vortices shed from the bluff body generates fluctuating electrical signals as a measure of fluid flow moving through the flow passage.     
     
     
       10. A combination as set forth in claim 9 wherein both extremities of the planar member are secured to the body. 
     
     
       11. A combination as set forth in claim 10 wherein the planar member includes a slit disposed in a midsection thereof partially separating the planar member into two halves. 
     
     
       12. A device for measuring fluid flow comprising in combination: (a) a body including a flow passage;   (b) a bluff body of elongated shape disposed across a first cross section of the flow passage;   (c) a planar member disposed partially across a second cross section of the fluid passage generally parallel to the bluff body on a plane generally parallel to the central axis of the flow passage wherein one extremity of the planar member is secured to the body at least in part and the other extremity opposite to said one extremity is terminated in the middle of the flow passage; and   (d) a transducer including a force receiving member connected to the terminated extremity of the planar member by a mechanical coupling that transmits stress from the planar member to the force receiving member and produces a bending moment in the force receiving member; wherein alternating lift force on the planar member associated with vortices shed from the bluff body generates fluctuating electrical signals as a measure of fluid flow moving through the flow passage.     
     
     
       13. The combination as set forth in claim 12 wherein the force receiving member includes a planar section disposed generally parallel to the planar member and extending into the flow passage.